| 摘要 |
<p>Method for the optical check of photomasks, consisting of glass plates with one-sided opaque structures, by a microscope, is based on directing a parallel beam of light against the underside while the microscope is focussed on a major plane of the mask. The angle of the incident light beam is varied in the horizontal and vertical plane to prevent its perpendicular incidence on the edges of the opaque structures. These edges therefore have little brilliance under the microscope but any scratched or foreign particles adhering to the photomask after usage are clearly marked by a strong contrast. This is a low-cost method of finding and localising defects in photomasks.</p> |
